LA³NET fellow Alex Alexandrova’s work on laser interferometry is published in Optical Engineering

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The manuscript "Laser Diode Self-mixing Interferometry for Velocity Measurements" by A. Alexandrova, V. Tzoganiz and C. Welsch has been published in the Optical Engineering journal. Laser self-mixing is usually used for measurement of low velocities and vibrations but this paper explores the proposal to use the method for the measurement of velocity and density of gas jets based on self-contained optical feedback.

Self-mixing interferometry has been applied to flow-velocity measurements often aimed at biological applications, such as blood flow characterisation, Brownian motion and biological species dynamic studies. There has been high interest in this area resulting in a number of works with measurements of relatively small velocity from 0.1 mm/s to 10 cm/s with high accuracy.

In the paper we demonstrate how higher velocities can be measured and show the impact of different target geometries and characteristics on the quality of the detected signal. We use this as a basis to assess the potential for future gas-jet characterisation applications which would be an entirely new application for this technique. A detailed investigation into different targets is presented covering velocity measurements of solid targets of up to 50 m/s and flow velocities of up to 1 m/s. Previous work related to self-mixing is more focused on the precision and spatial resolution of the method rather than the possibility of measuring high velocities and the presented results are entirely new. The measured velocities reported in literature using the SM technique rarely exceed 5 m/s with several works mentioning the movement of solid object by 25 m/s.

A.S. Alexandrova, V. Tzoganis and C.P. Welsch, "Laser diode self-mixing interferometry for velocity Measurements', Optical Engineering 54(3), 034104 (March 2015)